Current evidence suggests that the secretion of growth hormone and prolactin is influenced by releasing and inhibiting factors of hypothalamic origin, that hormone release may occur from physiologically separate intracellular pools, and that released hormone in vitro as well as in vivo exhibits molecular size heterogeneity. The plurality of intracellular pools and the variety of extrapituitary influences which may alter hormone release suggest the existence of multiple subcellular regulatory mechanisms which, when identified would lend themselves to pharmacologic manipulation. Therefore, simple measurement of stimulated or inhibited hormone release and pituitary hormone content are inadequate to study control mechanisms responsible for altered hormone release, storage, and synthesis. The applicant proposes to investigate qualitative and quantitative aspects of GH and Prl metabolism in normal, non-euthyroid and fetal pituitary and tumor tissue and by clarifying the pituitary's available range of responses to provide and assay by which the mechanism of action of physiologic and pharmacologic secretagogues can be identified. The central methodology is an in vitro perfusion system using rat anterior pituitaries, with or without rat hypothalami, exposed to (3H) and (14C) amino acids. (3H) and (14C) hormone synthesis, storage, and release will be examined by immunoprecipitation. The cell's response to physiologic and pharmacologic secretagogues as well as the effects of mediators and disruptors of subcellular mechanisms will be investigated. By analyzing qualitative, quantitative and temporal aspects of pituitary response, the applicant hopes to be able to distinguish between factors (secretagogues or inhibitors) whose effects are similar but whose mechanisms of action differ, and to be able to detect the simultaneous presence in tissue extracts of factors with opposite effects. Since individual hormones may be controlled by both stimulatory and inhibitory influences, and since individual neurohormones alter the release of several pituitary hormones, clarification of mechanisms of response assumes importance.